Vacuum cleaners which utilise cyclonic separators are well known. Examples of such vacuum cleaners are shown in EP 0 042 723, EP 1 370 173 and EP 1 268 076. In general, an airflow in which dirt and dust is entrained enters a first cyclonic separator via a tangential inlet which causes the airflow to follow a spiral or helical path within a collecting chamber so that the dirt and dust is separated from the airflow. Relatively clean air passes out of the chamber whilst the separated dirt and dust is collected therein. In some applications, and as described in EP 0 042 723, the airflow is then passed to a second cyclonic separator which is capable of separating finer dirt and dust than the first cyclonic separator. It has been found useful to position a barrier member, known as a shroud, between the outlet to the first cyclonic separator and the inlet to the second cyclonic separator.
A shroud typically includes a wall having a large number of passageways or through-holes which communicate on their upstream side with the separating chamber of the first cyclonic separator. The through-holes of the shroud thus form the outlet from the first cyclonic separator. In use, some of the dirt and dust not separated by the first cyclonic separator passes through the through-holes in the shroud and into the second cyclonic separator.
However, the greater the amount of dirt and dust which is pulled through the shroud with the airflow, the greater the work which has to be done by the second cyclonic separator to separate the remaining dirt and dust from the airflow. Further, the greater the amount of dirt and dust which passes through the through-holes in the shroud, the greater the risk of the through-holes in the shroud becoming blocked with dirt and dust. Blocked through-holes in a shroud can reduce the efficiency at which the vacuum cleaner operates. Therefore, the risk of blockages forming should be minimised. Consequently, it is beneficial to retain the maximum amount of dirt and dust within the first cyclonic separator and prevent as much dirt and dust as possible from passing through the through-holes in the shroud.
In order to reduce the amount of dirt and dust passing from the first cyclonic separator into other parts of a vacuum cleaner, it is known to provide angled passageways around the outlet from the first cyclonic separator. The passageways are angled away from the direction of airflow around the outlet such that the air has to turn through more than a right angle in order to pass through the passageways. Dirt and dust, having inertia considerably greater than that of air, is unable to turn as sharply. Consequently, the larger particles of dirt and dust do not pass through the passageways and remain in the first cyclonic separator. Examples of such arrangements are shown in EP 0 972 573 and GB 2 376 197. In these arrangements, a plurality of longitudinal blades are provided. The blades are angled away from the airflow to form a plurality of angled passageways. However, the blades define relatively long passageways which have a relatively large cross-sectional area in comparison to known shrouds comprising through-holes. This may allow unwanted dirt and dust to pass through the passageways.
It is an object of the invention to provide a shroud for separating apparatus in which the amount of dirt and dust which passes through the through-holes in the shroud is reduced in comparison to known prior art arrangements.